It is well known that when piloting an aircraft (airplane, helicopter and the like) in instrument meteorological conditions (IMC), or visual meteorological conditions (VMC), and the like, a systematic and thorough scanning and visual monitoring of the aircraft instruments is of utmost importance. In IMC, reliance upon and monitoring of the instrument panel is essential. In addition the pilot must remain aware of other conditions in the aircraft and maintain an ongoing search for air traffic and other potential hazards.
Presently, many instruments are available in an aircraft to provide information to the pilot as to the condition and flight characteristics of the aircraft at any given time. Such instruments provide information related to conditions such as altitude, headings, air speed, glide path, interception of radials, attitude of the aircraft and the like. All of these instruments must be monitored continuously to maintain an awareness of the condition of the aircraft to avoid potentially hazardous situations. At present, such monitoring is primarily done visually. Many of these instruments are so important that they are equipped with alarms, which may generate highly noticeable signals when extreme variations from a desired condition occur. These alarms may take the form of a loud noise, a flashing light, a combination thereof, or the like. Such signals may be used for failures to lower landing gear when the aircraft approaches a low altitude, for an air speed below a selected minimum, or the like. Such signals have typically been buzzers, beepers, horns, or other similar sounds. Such signals are not typically used until extreme conditions are noted. This presents a hazard since the occurrence of these extreme variations from desired conditions can result in difficulty in correcting the flight characteristic which has approached an extreme condition. Further, the signal of the extreme condition is generally set to indicate only a hazardous condition. Accordingly, there is no monitoring alarm or indication to warn the pilot of lesser variations from a selected condition prior to the occurrence of any extreme condition.
It would be highly desirable if a system could be provided which provided a continuous or substantially continuous audible notice to the pilot of small differences from a set value for selected flight characteristics so that such differences can be easily corrected before reaching a severe or hazardous difference from the set value.
In medical areas of endeavor, such as surgery, continuous aural monitoring of various medical patient symptoms has been used. These systems comprise the use of audio monitoring with various sounds and pitches, such as a pulsating sound at various pitches to reflect changes in a first condition with the pulse being modulated to reflect changes from a second desired condition. Since these monitoring systems have been used, the technology for the implementation of such systems is well known.
Similar problems occur in aircraft. In other words, the pilot must remain aware of a large number of variables during flight and it would be highly desirable if a system could be provided which would allow the pilot to remain continuously aware of selected key flight characteristics while engaged in otherwise monitoring the flight characteristics of the aircraft and other conditions related to the safe operation of the aircraft. Accordingly, a continuing effort has been directed to the development of improved methods for maintaining pilot awareness of critical conditions that may occur in an aircraft, either commercial or private.